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Nov. 4, 2011 -- Many people indulge far too often in trans-fat-heavy foods because it makes them feel good, even though they know these foods may not be good for their hearts and their waistlines.

But while that double cheeseburger or glazed doughnut might temporarily improve your mood, research from Spain suggests the feeling won’t last.

In a study published earlier this year, the Spanish research team found that people who ate the most trans fats also had the highest depression levels.

Now the researchers report that these people also had the lowest scores on tests designed to measure quality of life.

Trans Fats and Mental Health

Trans fats, also known as partially hydrogenated oils, are created in the lab in a process that adds hydrogen to liquid oils to make them more solid.

The fats are most commonly found in fried fast foods and heavily processed foods, such as commercially produced pastries, cookies, and crackers.

The newly published study was designed to determine if different types of dietary fats affected quality of life -- a term that encompasses functional health, well-being, and happiness.

More than 8,400 participants in an ongoing nutrition study in Spain were included in the latest analysis.

All the study participants completed a 136-item food questionnaire when they entered the study.

Four years later they also completed a widely used health survey designed to assess quality of life.

Tran fats were the only dietary fats that showed a significant association with self-reported quality of life scores, lead researcher Christina Ruano of the University of Las Palmas de Gram Canaria in Las Palmas, Spain, tells WebMD.

Study participants whose diets contained the most trans fats were also the most likely to report characteristics associated with a poorer quality of life, including feeling tired or worn out, having a negative attitude about work and social life, and having negative beliefs about their future health.

The study was published online this week in Nutrition Journal.

‘Trans Fats Markers for Poor Diet’

The study participants were all college educated and the average daily intake of trans fats within the group was about half that of the Spanish population as a whole and one-fourth that of the average American.

“Because of this, we believe the association could be even more robust in other populations, where more trans fats are eaten,” Ruano says.

While the researchers attempted to take into account other factors that could influence quality of life, New York University professor of nutrition Marion Nestle, PhD, MPH, says it is far from clear if trans fat intake has a direct impact on well-being.

“Trans fats are a marker for poor diets with lots of junk foods,” she tells WebMD in an email. “That has to be factored in.”